imagine, if you can, what the angular gap between each one would be.
a typical train rail is 39ft long.
half of that = 19.5 ft
the earth's radius on average is 3,959 mi = 20,903,520 ft ((at sea level -- this number is bigger at any elevation above))
so the angle between each track joined end-to end on level ground is less than:
sin(19.5 / 20,903,520) = 0.000000016 degrees
this is how much you're suggesting railroad engineers 'take into account' when they lay track.
this geometry is using a triangle instead of a pie-slice, so the track would be shorter than the actual curved surface. the arc that subtends this angle should be s = r*theta = 0.000063 feet
that's about 2 hundredths of a millimeter.
that's how far off the length of a 39 ft length of rail would be from the distance it's supposed to cover on the globe -- but guess how that compares to manufacturing discrepancy in the actual length of the rail, and how that compares to the gap built into the track for thermal expansion?
one word, very common in engineering: negligible